The combustion chamber of a rocket engine reaches very high temperatures as the rocket engine's propellants are ignited and burned inside the chamber and the burned gases are expelled through the rocket engine nozzle. The temperature of the burning propellants inside the combustion chamber is normally well above the temperature at which the combustion chamber would melt. Accordingly, rocket engines must be cooled during operation of the engine in order to preserve the combustion chamber.
Typically rocket engines utilize regenerative cooling to cool the combustion chamber. In an engine with regenerative cooling, at least one of the propellants is circulated through the walls of the combustion chamber before it is injected into the combustion chamber to be ignited. The circulating propellants absorb heat from the walls of the combustion chamber, cooling the combustion chamber to a suitable temperature. This cooling is termed “regenerative” because the heat energy absorbed by the propellants is not lost; rather, the heated propellants recycle the heat energy into the combustion chamber when they are injected into the chamber to be burned.
In order to introduce regenerative cooling into the walls of a combustion chamber, combustion chambers can be constructed with an inner wall and an outer wall bonded together. The inner wall forms the inside of the combustion chamber. The propellants circulate through a series of flow passages or grooves formed between the inner and outer walls. However, the inner wall reaches a higher temperature than the outer wall, as the inner wall is closer to the high heat inside the combustion chamber. As a result, the thermal expansions of the two walls differ, with one expanding more than the other. Therefore, the combustion chamber experiences high thermal stresses and thermal cyclic fatigue which can ultimately cause failure of the combustion chamber. Accordingly, it is desirable to provide a rocket engine combustion chamber that utilizes regenerative cooling while reducing thermal stresses in the combustion chamber.